Preparation of Ni–Cu–Mo–Cr film deposited on AZ31magnesium alloy by double glow sputtering with Cu interlayer

For improving the corrosion resistance of AZ31magnesium alloy, a double glow sputtering deposited Ni–Cu–Mo–Cr film with brush plating Cu interlayer is applied to deposit a metal amorphous/nanocrystal film on AZ31magnesium alloy. Using a brush plated Cu interlayer, the content of noble elements, such as Ni, Cr, and Mo, is higher than that of a Ni-based film without Cu interlayer. The microstructure of the Ni–Cu–Mo–Cr alloy film with the brush plated Cu interlayer confirms that the film is classified into two regions, i.e., an amorphous layer on the outmost surface and an underlying nanocrystalline layer with a grain size of less than 5 nm. The Ni-based alloy amorphous film formed on AZ31magnesium alloy was investigated using an electrochemical polarization measurement. Compared with the AZ31 magnesium alloy, the sputter-deposited Ni-based alloy film and the sputter-depostion Ni-based alloy film with a brush plated Cu interlayer formed on AZ31 magnesium alloy exhibit obvious passivation phenomena.